Radio tag reading apparatus and control method

ABSTRACT

In one embodiment, a radio tag reading apparatus has an antenna device, a storage device, and a controller. The controller judges what frequency band is usable or not out of a plurality of frequency bands stored in the storage device. Further the controller makes the antenna device radiate a radio wave in the judged usable frequency band at a transmission rate in accordance with a width of the judged usable frequency band.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.15/839,067, filed on Dec. 12, 2017, which is based upon and claims thebenefit of priority from the prior Japanese Patent Application No.2016-247048, filed on Dec. 20, 2016, the entire contents of each ofwhich are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a radio tag readingapparatus and a control method thereof.

BACKGROUND

Recently, there exists a radio tag reading apparatus which readsinformation from a radio tag attached to a commodity, in a store such asa clothing store, using RFID (Radio Frequency Identification)technology, for example. This radio tag reading apparatus readscommodity information and so on from a radio tag attached to acommodity. For the reason, a store reads commodity information fromradio tags attached to commodities displayed on a shelf or the like andcommodities housed in a box, using the radio tag reading apparatus, toperform management of a stock status of the commodities in the store. Inaddition, the radio tag reading apparatus is also widespread in businessworlds other than clothes.

An operator of a store trains a handy type radio tag reading apparatuson a radio tag attached to a commodity such as clothes displayed on ashelf, and radiates a radio wave for information reading from the radiotag reading apparatus, and receives a response radio wave from the radiotag, to receive information from the radio tag. And, when radiating theradio wave toward the radio tag, the radio tag reading apparatusperforms carrier sense so as to avoid interference with a radio wavewhich is being radiated from another radio tag reading apparatus, andthereby executes radiation of the radio wave using an unused channel.

Incidentally, it takes a definite time for a radio tag reading apparatusto read information of a radio tag. For the reason, when the number ofthe radio tags to be read is large, it takes a great deal of time forreading information of all the radio tags.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing an outer appearance of a radio tag readingapparatus according to an embodiment.

FIG. 2 is a block diagram showing a hardware configuration of the radiotag reading apparatus according to the embodiment.

FIG. 3 is a diagram showing a memory map of the storage device accordingto the embodiment.

FIG. 4 is a diagram showing the relation between a frequency band of aradio wave which the radio tag reading apparatus according to theembodiment transmits using all the frequency bands and a power thereof.

FIG. 5 is a diagram showing the relation between a frequency band of aradio wave which the radio tag reading apparatus according to theembodiment transmits using one of the vacant frequency bands and a powerthereof.

FIG. 6 is a block diagram showing a hardware configuration of a radiotag according to the embodiment.

FIG. 7 is a block diagram showing a functional configuration of theradio tag reading apparatus according to the embodiment.

FIG. 8 is a flow chart showing a control processing of a radio tagreading apparatus according to a first embodiment.

FIG. 9 is a flow chart showing a part of a control processing of a radiotag reading apparatus according to a second embodiment.

FIG. 10 is a diagram showing a memory map of a storage device accordingto a third embodiment.

FIG. 11 is a diagram showing the relation between another frequency bandof a radio wave which the radio tag reading apparatus according to thethird embodiment transmits and a power thereof.

FIG. 12 is a flow chart showing a part of a control processing of aradio tag reading apparatus according to the third embodiment.

DETAILED DESCRIPTION

According to one embodiment, the radio tag reading apparatus radiates aradio wave to a radio tag, to receive information of the radio tag. Theradio tag reading apparatus has an antenna device, a storage device, anda controller. The antenna device radiates the radio wave toward theradio tag and receives a response radio wave from the radio tag. Thestorage device stores a plurality of frequency bands sorted intofrequency bands in which the radio wave can be radiated. The controllerhas a processor and a memory, and as a result that the processorexecutes a program stored in the memory, judges what frequency band isusable or not out of the plurality of frequency bands stored in thestorage device. The controller makes the antenna device radiate theradio wave in the judged usable frequency band at a transmission rate inaccordance with a width of the judged usable frequency band, to executecommunication with the radio tag.

First Embodiment

Hereinafter, a radio tag reading apparatus of a first embodiment and acontrol method thereof will be described in detail with reference toFIG. 1 to FIG. 8. In the drawings, the same symbols indicate the same orsimilar portions. Further, in the first embodiment described below, theradio tag reading apparatus will be described using a handy type radiotag reading apparatus. In addition, in the first embodiment, an exampleof an apparel shop for selling clothes will be described as an exampleof a store, but the store may be a store for selling other commodities.The radio tag reading apparatus described below is not limited to theembodiment.

FIG. 1 is a side view of a radio tag reading apparatus 1 according tothe first embodiment which is seen from a side surface thereof. Theradio tag reading apparatus 1 radiates a radio wave to a radio tag ST(refer to FIG. 6) attached to a commodity, and receives information ofthe commodity from each radio tag, to collect the information of thecommodity. In addition, the radio tag reading apparatus 1 radiates aradio wave including information of a commodity to a radio tag attachedto the commodity, to write the information of the commodity into theradio tag ST.

As shown in FIG. 1, the radio tag reading apparatus 1 has a main body 2,an antenna device 3, a grip 4 and a trigger switch 5. The antenna device3 is arranged at a front side in the radiation direction of the radiowave in the main body 2. When the radio tag reading apparatus 1 isoperated, the grip 4 is gripped by an operator. The grip 4 is arrangedbehind the antenna device 3 in the main body 2. The antenna device 3 hasa plane portion 39 at a foremost portion thereof. In addition, theantenna device 3 incorporates an antenna 33 formed in a plane shape of asubstantially square shape therein. The antenna 33 is provided inapproximately parallel with the plane portion 39.

The trigger switch 5 is incorporated in the grip 4. The trigger switch 5is a switch for radiating/stopping a radio wave from the antenna 3. Whenan operator pulls and operates the trigger switch 5 while gripping thegrip 4, the radio tag reading apparatus 1 radiates a radio wave from theantenna device 3 (the antenna 33). The radio tag ST receives the radiowave radiated from the antenna device 3 of the radio tag readingapparatus 1, and transmits a response wave. The response wave includesinformation of a commodity to which the radio tag ST is attached. Inaddition, the radio tag reading apparatus 1 receives the response wavefrom the radio tag ST by the antenna 33 of the antenna device 3. Whenthe operator releases the operation of the trigger switch 5, the radiotag reading apparatus 1 stops radiating the radio wave from the antennadevice 3. In addition, the radio tag reading apparatus 1 has anoperation unit 22 for performing various operations and a display unit21 for performing various displays on upper portions thereof.

Next, a circuit configuration of the radio tag reading apparatus 1 willbe described using FIG. 2. A controller 30 for main control is mountedon the main body 2. The controller 30 has a processor including a CPU(Central Processing Unit) 36 which functions as a control subject, a ROM(Read Only Memory) 37 which mainly stores a program, and a RAM (RandomAccess Memory) 38 which temporarily stores various data and so on.

The CPU 36 operates in accordance with a control program which has beenstored in the ROM 37 or a storage device 31 and has been developed inthe RAM 38, and thereby the controller 30 executes a control processingdescribed later. The display unit 21, the operation unit 22, the storagedevice 31 including a HDD (Hard Disc Drive) or a nonvolatile memory suchas a flash memory, a radio unit 32, a communication I/F 35 are connectedto this controller 30. In addition, an A/D converter 34 for A/Dconverting an output (an analog value) of the trigger switch 5 is alsoconnected to the controller 30. When an ON signal generated as a resultthat the trigger switch 5 has been operated is inputted to thecontroller 30, the controller 30 makes the antenna 30 radiate a radiowave for collecting information stored in the radio tag ST. In addition,though not shown in the drawing, the radio tag reading apparatus 1incorporates a battery for driving the respective circuits.

The storage device 31 includes the hard disc drive or the nonvolatilememory such as a flash memory, and stores the control program and inputdata. In addition, though the storage device 31 will be described laterin detail, it stores vacant (usable) channels and frequency bands inassociation.

The radio unit 32 has a D/A converter 32 a, a radiation circuit 32 b, areception circuit 32 c, an A/D converter 32 d, a transmission/receptionswitch 32 e. The D/A converter 32 a performs D/A conversion of radiationdata and control data from the controller 30 by separate systems, andsupplies the D/A converted data to the radiation circuit 32 b.

The radiation circuit 32 b performs prescribed modulation and outputpower adjustment of the inputted radiation data, and outputs a modulatedsignal to the antenna 33 via the transmission/reception switch 32 e forswitching between radiation and reception. On the other hand, a responsesignal (a response radio wave) from the radio tag ST which has beenreceived by the antenna 33 is supplied to the reception circuit 32 c viathe transmission/reception switch 32 e. And the reception circuit 32 cdemodulates the response signal. The demodulated response signal is A/Dconverted by the A/D converter 32 d and is supplied to the controller30.

The communication I/F 35 transmits information to a store server (notshown), and receives information from the store server, using radiocommunication. The store server manages sales information and stockinformation of commodities.

Next, the relation between a vacant channel and a frequency band to beused which have been stored in the storage device 31. In the firstembodiment, the radio tag reading apparatus 1 radiates radio waves usingthree channels of A1, A2, A3. Frequency bands of radio waves which theradio tag reading apparatus 1 radiates are set for the respectivechannels.

FIG. 3 shows the relation between a vacant channel and a frequency bandto be used in a memory map stored in the storage device 31. The storagedevice 31 has a channel section 311 and a frequency band section 312.The channel section 311 stores a kind of a channel which the radio tagreading apparatus 1 can use (which is not used by another radio tagreading apparatus 1, and is vacant). The frequency band section 312stores a frequency band to be used corresponding to the channel storedin the channel section 311.

In the case of the first embodiment, when a vacant channel is thechannel A1, the radio tag reading apparatus 1 radiates a radio wave setin a frequency band A (a second frequency band). In this case, atransmission rate of the radio wave which the radio tag readingapparatus 1 radiates is a low speed (a second transmission rate). Inaddition, when a vacant channel is the channel A2, the radio tag readingapparatus 1 radiates a radio wave set in a frequency band B (the secondfrequency band). In this case, a transmission rate of the radio wavewhich the radio tag reading apparatus 1 radiates is the low speed (thesecond transmission rate). In addition, when a vacant channel is thechannel A3, the radio tag reading apparatus 1 radiates a radio wave setin a frequency band C (the second frequency band). In this case, atransmission rate of the radio wave which the radio tag readingapparatus 1 radiates is the low speed (the second transmission rate).

In addition, when vacant channels are the channels A1 and A2, the radiotag reading apparatus 1 radiates a radio wave in any one frequency bandof the frequency band A and the frequency band B. In this case, atransmission rate of the radio wave which the radio tag readingapparatus 1 radiates is the low speed (the second transmission rate). Inaddition, when vacant channels are the channels A2 and A3, the radio tagreading apparatus 1 radiates a radio wave in any one frequency band ofthe frequency band B and the frequency band C. In this case, atransmission rate of the radio wave which the radio tag readingapparatus 1 radiates is the low speed (the second transmission rate).

When vacant channels are the channels A1, A2, A3, the radio tag readingapparatus 1 radiates a radio wave in a frequency band D (a firstfrequency band) that is the frequency band A+the frequency band B+thefrequency band C. In this case, in accordance with publicly-knownShannon-Hartley theorem, a frequency band of the frequency band D iswider than the frequency band A, the frequency band B, and the frequencyband C. For the reason, a transmission rate of the radio wave can be setto a high speed. Accordingly, a transmission rate of the radio wavewhich the radio tag reading apparatus 1 radiates is a high speed (afirst transmission rate).

Here, a width of a frequency band of a radio wave which the radio tagreading apparatus 1 radiates and a transmission rate of the radio wavewhich can be set. For a radio wave in a frequency band which has beenwiden, a transmission rate of the radio wave can be set faster. For aradio wave in a frequency band which has been narrowed, only a slowtransmission rate can be set.

Next, a usable frequency band and a power will be described. FIG. 4 is adiagram showing the relation between a frequency band of a radio wavewhich the radio tag reading apparatus 1 transmits and a power thereof,when all the channels are vacant (usable). As shown in FIG. 4, when thechannel A1, the channel A2, and the channel A3 are all vacant, forexample, the radio tag reading apparatus 1 transmits a radio wave 1using the frequency band D (the first frequency band) including all thechannels. This radio wave 1 is transmitted at the first transmissionrate with a fast transmission rate.

Next, a case in which any one of the channel A1, the channel A2, thechannel A3 is used will be described using FIG. 5. In the example ofFIG. 5, the channel A1 is a frequency band which is being used (awaveform of a dashed line). For the reason, the radio tag readingapparatus 1 transmits a radio wave (a waveform of a solid line) usingthe frequency band B corresponding to the vacant channel A2. This radiowave 2 is transmitted at the second transmission rate with a slowtransmission rate. In addition, the radio tag reading apparatus 1 maytransmit the radio wave 2 in the frequency band C, using the vacantchannel A3.

Next, the radio tag ST will be described using FIG. 6. The radio tag SThas an antenna 41, a transmission/reception unit 42, a control unit 43,an electromotive force unit 44, a memory 45. The control unit 43controls the transmission/reception unit 42, the electromotive forceunit 44, and memory 45. The antenna 41 receives the radio wave radiatedfrom the antenna 33 of the radio tag reading apparatus 1. Thetransmission/reception unit 42 controls transmission/reception of theradio wave by the antenna 41. The electromotive force unit 44 generatespower for starting up the radio tag ST, and for performing control suchas transmitting information to the radio tag reading apparatus 1, basedon the radio wave from the radio tag reading apparatus 1 which has beenreceived by the antenna 41. The memory 45 stores commodity informationof a commodity S to which the radio tag ST is attached, and radio taginformation for identifying the relevant radio tag ST.

Subsequently, a control processing of the radio tag reading apparatus 1according to the first embodiment will be described using FIG. 7, FIG.8. FIG. 7 is a functional block diagram showing a functionalconfiguration of the radio tag reading apparatus 1. The CPU 36 operatesin accordance with the various programs including the control programstored in the ROM 37 and so on, and thereby the controller 30 functionsas a judgement module 301, an execution module 302.

The judgement module 301 has a function to judge a use state of anotherradio tag reading apparatus which reads information of a radio tag in afrequency band in which the radio wave can be radiated, and to judge ausable frequency band.

The execution module 302 has a function to perform communication withthe radio tag at a transmission rate in accordance with a width of theusable frequency band which has been judged by the judgement module 301.

FIG. 8 is a flow chart showing a control processing of the radio tagreading apparatus 1 in the first embodiment. As shown in FIG. 8, in astep S11, the controller 30 sets a frequency band of a radio wave to beradiated (hereinafter simply called a frequency band thereof) to thefrequency band D that is the first frequency band. Next, in a step S12,the controller 30 sets a transmission rate of the radio wave to beradiated to the high speed (the first transmission rate). And, in a stepS13, the controller 30 examines (carrier senses) whether or not afrequency band which has been used already is present in the frequencyband D. Specifically, the controller 30 examines whether or notinterference with a radio wave (hereinafter called another radio wave)radiated from another radio tag reading apparatus 1 is generated, beforeradiating the radio wave in the frequency band D. This examinationmethod is performed by a previously known method.

Next, in a step S14, the controller 30 (the judgment module 301) judgeswhether or not all the frequency bands in the frequency band D arevacant, that is, whether or not all the channels are usable. Whenjudging that the interference with the another radio wave is notgenerated in the frequency band D, as a result of the above-describedexamination, the controller 30 judges that all the channels are vacant(usable). When judging that the interference with the another radio waveis generated in the frequency band D, the controller 30 judges that allthe channels are not vacant (a part of the channels is already used).When it is judged by the controller 30 (the judgment module 301) thatall the channels are vacant (Yes in step S14) the processing of thecontroller 30 transfers to a step S15. In the step S15, the controller(the execution module 302) radiates the radio wave 1 at the high speedin the frequency band D, to execute radio communication with the radiotag ST. In the processing of this step S15, the controller 30 receivesinformation (commodity information, for example) from the radio tag ST.And the controller 30 finishes the processing.

On the other hand, when it is judged by the controller 30 that all thechannels are not vacant (No in step S14), the processing of thecontroller 30 transfer to a step S21. In the step S21, the controller 30sets a frequency band thereof to the frequency band A of the channel A1.Next, in a step S22, the controller 30 sets a transmission rate of aradio wave to be radiated to the low speed (the second transmissionrate). And, in a step S23, the controller 30 examines whether or not thefrequency band A is used already. This examination is the sameexamination as the step S13.

And, in a step S24, the controller 30 (the judgment module 301) judgeswhether or not the channel A1 is vacant. When it is judged by thecontroller 30 that the channel A1 is vacant (Yes in step S24), theprocessing of the controller 30 transfers to the step S15. In the stepS15, the controller 30 radiates the radio wave 2 at the low speed in thefrequency band A, to execute radio communication with the radio tag ST.In the processing of this step S15, the controller 30 receivesinformation (commodity information, for example) from the radio tag ST.And the controller 30 finishes the processing.

In addition, when it is judged by the controller 30 that the channel A1is not vacant (is used already) (No in step S24), the processing of thecontroller 30 transfers to a step S25. In the step S25, the controller30 judges whether or not use states in all the channels of the channelA1, the channel A2, and the channel A3 have been confirmed. Thecontroller 30 stores the channel set in the step S21 and the channeljudged in the step S24, to execute the judgment of the step S25. When itis judged by the controller that all the channels have not beenconfirmed yet (No in step S25), the processing of the controller 30transfers to a step S26. In the step S26, the controller 30 designatesand sets the next channel. And the processing of the controller 30returns to the step S23, and the controller 30 executes the examination.And the controller 30 repeats the judgment processings of the step S24and the step S25. In this case, in the processing of each of the stepsS15, the radio wave is radiated at the low speed in the above-describedset frequency band.

On the other hand, when it is judged by the controller 30 that the usestates in all the channels have been judged in the step S25 (Yes in stepS25), the processing of the controller 30 transfers to a step S27. Sinceall the channels are already in the use states, in the step S27, thecontroller 30 displays a message indicating that communication with theradio tag ST is not available on the display unit 21. And the controller30 finishes the processing.

According to the first embodiment like this, when all the channels(frequency bands) are vacant (usable), the controller 30 sets atransmission rate of a radio wave to the high speed and radiates theradio wave, to collect information from the radio tag. For the reason,even when the number of the radio tags to be read is large, it ispossible to shorten a read time of the radio tag. In addition, the firstembodiment is effective when the number of the radio tag readingapparatuses 1 to be used simultaneously is relatively small (theinterference is not relatively generated).

Second Embodiment

From here on, a second embodiment will be described. In the firstembodiment, the radio tag reading apparatus 1 has firstly examined a usestate of a radio wave by another radio tag reading apparatus 1 using thefrequency band D. In contrast, in the second embodiment, the radio tagreading apparatus 1 firstly examines the frequency band A of the channelA1, the frequency band B of the channel A2, the frequency band C of thechannel A3 individually, and if the channel A1, the channel A2, thechannel A3 are all usable, the radio tag reading apparatus 1 sets afrequency band thereof to the frequency band D assuming that all thechannels are vacant.

FIG. 9 is a flow chart showing a control processing of the radio tagreading apparatus 1 in the second embodiment. As shown in FIG. 9, in astep S31, the controller 30 firstly sets a frequency band thereof to thefrequency band A that is the frequency band of the channel A1. And in astep S32, the controller 30 examines whether or not the channel A1 isalready used based on whether or not the radio wave interference isgenerated. This examination is the same examination as the step S13.Similarly, in a step S33, the controller 30 sets a frequency bandthereof to the frequency band B that is the frequency band of thechannel A2. And in a step S34, the controller 30 examines whether or notthe channel A2 is already used. This examination is the same examinationas the step S13. Similarly, in a step S35, the controller 30 sets afrequency band thereof to the frequency band C that is the frequencyband of the channel A3. And in a step S36, the controller 30 examineswhether or not the channel A3 is already used. This examination is thesame examination as the step S13.

Next, in a step S41, the controller 30 (the judgment module 301) judgeswhether or not all the channels are vacant (usable), based on theexaminations of the step S32, the step S34, the step S36. As a result ofthe examinations of the step S32, the step S34, the step S36, when theinterference with another radio wave is not generated in any of thechannels, the controller 30 judges that all the channels are vacant. Asa result of the examinations of the step S32, the step S34, the stepS36, when the interference with another radio wave is generated in anyof the channels, the controller 30 judges that all the channels are notvacant.

When it is judged by the controller 30 that all the channels are vacant(Yes in step S41), in a step S42, the controller 30 sets a frequencyband thereof to the frequency band D. And, in a step S43, the controller30 sets a transmission rate of a radio wave to be radiated to the highspeed (the first transmission rate). And, in a step S44, the controller30 (the execution module 302) radiates the radio wave 1 at the highspeed in the frequency band D, to execute radio communication with theradio tag ST. And the controller 30 finishes the processing.

On the other hand, when it is judged by the controller 30 that all thechannels are not vacant (No in step S41), the processing of thecontroller 30 transfers to a step S45. In the step S45 the controller 30(the judgment module 301) judges whether or not a vacant channel ispresent. As a result of the examinations of the step S32, the step S34,the step S36, when a channel in which the interference with anotherradio wave is not generated is present, the controller 30 judges that avacant channel is present. As a result of the examinations of the stepS32, the step S34, the step S36, when the interference with anotherradio wave is generated in all the channels, the controller 30 judgesthat a vacant channel is not present.

When it is judged by the controller 30 that a vacant channel is present(Yes in step S45), the processing of the controller 30 transfers to astep S46. In the step S46, the controller 30 sets a frequency bandthereof to the frequency band corresponding to the one vacant channel.And in a step S47, the controller 30 sets a transmission rate of a radiowave to be radiated to the low speed (the second transmission rate).And, in the step S44, the controller 30 radiates the radio wave 2 at thelow speed in the set frequency band, to execute radio communication withthe radio tag ST. And the controller 30 finishes the processing.

In addition, in the step S45, when it is judged that (No in step S45),the processing of the controller 30 transfers to a step S48. In the stepS48, the controller 30 displays a message indicating that communicationwith the radio tag ST is not available on the display unit 21. And thecontroller 30 finishes the processing.

According to the second embodiment like this, when all the channels(frequency bands) are vacant (usable), the controller 30 sets atransmission rate of a radio wave to the high speed and radiates theradio wave, to collect information from the radio tag. For the reason,even when the number of the radio tags to be read is large, it ispossible to shorten a read time of the radio tag. In addition, thesecond embodiment is effective when the number of the radio tag readingapparatuses to be used simultaneously is relatively large (theinterference is relatively easily generated).

Third Embodiment

From here on, a third embodiment will be described using FIG. 10-FIG.12. In the first embodiment and the second embodiment, when theinterference with a radio wave is generated, the radio tag readingapparatus 1 has radiated the radio wave 2 of the transmission rate ofthe low speed. In the third embodiment, when the interference with theradio wave is generated, the radio tag reading apparatus 1 furtherexamines whether or not consecutive vacant channels are present, andwhen the consecutive vacant channels are present, the radio tag readingapparatus 1 sets a frequency band thereof to the consecutive frequencybands using the consecutive channels. In addition, the radio tag readingapparatus 1 sets a transmission rate of a radio wave to a medium speed(a third transmission rate) that is a speed slower than the high speedand faster than the low speed.

FIG. 10 shows the relation between a vacant channel and a frequency bandto be used in a memory map stored in the storage device 31 according tothe third embodiment. In FIG. 10, the same symbols are given to the sameportions shown in FIG. 3, and the description thereof will be simplifiedor omitted.

In the third embodiment, when a vacant channel is A1, or a vacantchannel is A2, or a vacant channel is A3, the radio tag readingapparatus 1 radiates a radio wave in a frequency band corresponding tothe relevant vacant channel. In this case, a transmission rate of theradio wave which the radio tag reading apparatus 1 radiates is the lowspeed (the second transmission rate).

In addition, when vacant channels are the consecutive channels A1 andA2, the radio tag reading apparatus 1 radiates a radio wave in aconsecutive frequency band E obtained by combining the frequency band Aand the frequency band B. In this case, a frequency band of thefrequency band E is wider than the frequency band A, the frequency bandB, the frequency band C. However, a frequency band of the frequency bandE is narrower than a frequency band of the frequency band D. For thereason, it is possible to set a transmission rate of the radio wave tothe medium speed that is faster than the low speed and slower than thehigh speed. Accordingly, a transmission rate of the radio wave which theradio tag reading apparatus 1 radiates is the medium speed (the thirdtransmission rate). In addition, when vacant channels are A2 and A3, theradio tag reading apparatus 1 radiates a radio wave in a consecutivefrequency band F obtained by combining the frequency band B and thefrequency band C. Also in this case, a transmission rate of the radiowave which the radio tag reading apparatus 1 radiates is the mediumspeed (the third transmission rate).

Next, a case in which one channel is used and consecutive two channelsare vacant will be described using FIG. 11. In the example of FIG. 11,the channel A1 is used (a waveform of a dashed line). For the reason,the radio tag reading apparatus 1 transmits a radio wave 3 (a waveformof a solid line) using the consecutive frequency band F corresponding tothe vacant channels A2 and A3. This radio wave 3 is transmitted at atransmission rate of the medium speed (the third transmission rate).

Next, a control of the radio tag reading apparatus 1 according to thethird embodiment will be described. FIG. 12 is a flow chart showing apart of a control processing of the radio tag reading apparatus 1. InFIG. 12, since the steps S31-S36, the steps S41-S45, and the step S48perform the same control processings as FIG. 9, the description thereofwill be omitted.

In addition, in the step S45, when it is judged by the controller 30that a vacant channel is present (Yes in step S45), the processing ofthe controller 30 transfers to a step S51. In the step S51, thecontroller 30 (the judgment module 301) judges whether or not two ormore vacant channels with consecutive frequency bands are present. Whenit is judged by the controller 30 that two or more consecutive vacantchannels are present (Yes in step S51), the processing of the controller30 transfers to a step S52. In the step S52, the controller 30 sets afrequency band thereof to a third frequency band corresponding to theconsecutive channels. And in a step S53, the controller 30 sets atransmission rate of the radio wave to the transmission rate of themedium speed. And, in the step S44, the controller 30 (the executionmodule 302) radiates the radio wave 3 at the medium speed in the setfrequency band, to execute radio communication with the radio tag ST.And the controller 30 finishes the processing.

In addition, when it is judged by the controller 30 that two or moreconsecutive vacant channels are not present (No in step S51), thecontroller 30 executes the processings of the step S46 and the step S47.The processings of the step S46 and the step S47 are the sameprocessings as the step S46 and the step S47 of the second embodiment.

According to the third embodiment like this, when all the channels(frequency bands) are vacant (usable), the controller 30 sets atransmission rate of a radio wave to the high speed and radiates theradio wave, to collect information from the radio tag. For the reason,even when the number of the radio tags to be read is large, it ispossible to shorten a read time of the radio tag. In addition, the thirdembodiment is effective when the number of the radio tag readingapparatuses 1 to be used simultaneously is relatively large (theinterference is relatively easily generated).

In addition, according to the third embodiment, when a plurality ofconsecutive channels are vacant, the controller 30 sets a transmissionrate of a radio wave to the third transmission rate that is slower thanthe first transmission rate and faster than the second transmissionrate. For the reason, even when the number of the radio tags to be readis large, it is possible to make a read time of the radio tag relativelyshort.

For example, in the embodiments, three channels have been used, but anynumber of channels may be used if the number of the channels is not lessthan 2.

In addition, in the embodiments, three kinds of rates of the firsttransmission rate, the second transmission rate, and the thirdtransmission rate have been used, but any number of kinds of rates maybe used if the number of the rates is not less than 2.

In addition, in the embodiments, the radio tag reading apparatus 1 to beused in an apparel shop for selling clothes has been described, butwithout being limited to this, the embodiments may be applied to theradio tag reading apparatus 1 to be used in a store, a warehouse or thelike where a radio tag can be used.

In addition, in the third embodiment (the flow chart of FIG. 12), thesame control processing as the second embodiment (the flow chart of FIG.9) has been executed, but the same control processing as the firstembodiment (the flow chart of FIG. 8) may be executed.

In this case, after the step S24 (Yes in step S24), the judgmentprocessing of the step S51 and the processings of the steps S46, S47,S52, S53 have only to be executed.

In addition, the program to be executed in the radio tag readingapparatus 1 of the embodiments is provided while being recorded in acomputer readable recording medium, such as a CD-ROM, a flexible disk(FD), a CD-R, a DVD (Digital Versatile Disk) in a file of an installableformat or an executable format.

In addition, the program to be executed in the radio tag readingapparatus 1 of the embodiments may be stored on a computer connected toa network such as Internet, and may be provided by being downloadedthrough the network. In addition, the program to be executed in theradio tag reading apparatus 1 of the embodiments may be may be providedor distributed via a network such as Internet.

In addition, the program to be executed in the radio tag readingapparatus 1 of the embodiments may be provided while being previouslyincorporated in a ROM or the like.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A radio tag reading apparatus for radiating aradio wave to a radio tag for receiving information from the radio tag,comprising: an antenna device which radiates a radio wave toward a radiotag and receives a response radio wave from the radio tag; a storagedevice which stores a first frequency band including all of thefrequency bands in which the radio wave can be radiated and a pluralityof second frequency bands obtained by sorting the first frequency band;and a processor configured to: when the first frequency band is notusable and at least one second frequency band out of the plurality ofsecond frequency bands is usable, judge whether two or more consecutivesecond frequency bands out of the plurality of second frequency bandsare usable, and make the antenna device radiate the radio wave within ajudged usable frequency band at a transmission rate in accordance with awidth of the judged usable frequency band to execute communication withthe radio tag.
 2. The radio tag reading apparatus according to claim 1,wherein the processor is configured to: judge whether or not the firstfrequency band is usable, when the first frequency band is judged notusable, judge whether or not any second frequency band is usable, andwhen the first frequency band is judged not usable, judge whether two ormore consecutive second frequency bands out of the plurality of thesecond frequency bands are usable.
 3. The radio tag reading apparatusaccording to claim 2, wherein when the first frequency band is judgedusable, the processor is configured to make the antenna device radiatethe radio wave in the first frequency band at a high speed firsttransmission rate.
 4. The radio tag reading apparatus according to claim3, wherein when the first frequency band is judged not usable and atleast one second frequency band out of the plurality of second frequencybands is judged usable, the processor is configured to make the antennadevice radiate the radio wave in the judged usable second frequency bandat a second transmission rate slower than the first transmission rate.5. The radio tag reading apparatus according to claim 1, wherein theprocessor is configured to: execute a first judgment to judge,respectively, whether or not each second frequency band in the pluralityof second frequency bands is usable, execute a second judgment to judgewhether or not all second frequency bands of the plurality of secondfrequency bands are usable based on a result of the first judgment, andwhen not all of the second frequency bands of the plurality of secondfrequency bands are judged usable based on a result of the secondjudgment, execute a third judgment to judge whether or not any of thesecond frequency bands out of the plurality of second frequency bands isusable.
 6. The radio tag reading apparatus according to claim 5, whereinwhen all of the plurality of second frequency bands are usable, based onthe result of the second judgment, the processor is configured to makethe antenna device radiate the radio wave in the first frequency band ata high speed first transmission rate.
 7. The radio tag reading apparatusaccording to claim 6, wherein when at least one second frequency bandout of the plurality of second frequency bands is usable, based on theresult of the third judgment, the processor is configured to make theantenna device radiate the radio wave in the at least one secondfrequency band at a second transmission rate slower than the firsttransmission rate.
 8. The radio tag reading apparatus according to claim6, wherein when the at least one second frequency band out of theplurality of second frequency bands is usable, based on the result ofthe third judgment, the processor is configured to execute a fourthjudgment to judge whether or not two or more consecutive secondfrequency bands out of the plurality of second frequency bands areusable.
 9. The radio tag reading apparatus according to claim 8, whereinwhen two or more consecutive second frequency bands are not usable,based on a result of the fourth judgment, the processor is configured tomake the antenna device radiate the radio wave in only one judged usablesecond frequency band at a second transmission rate slower than thefirst transmission rate.
 10. The radio tag reading apparatus accordingto claim 9, wherein when two or more consecutive second frequency bandsare judged usable, based on the result of the fourth judgment, theprocessor is configured to make the antenna device radiate the radiowave in a frequency band including the two or more consecutive secondfrequency bands at a third transmission rate slower than the firsttransmission rate and faster than the second transmission rate.